JPH0513263B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a method of measuring the depth of surface opening defects generated in various solids using ultrasonic waves. The solid surface opening defect referred to here is a defect that occurs in parts or members that constitute equipment in various industrial fields, such as electrical equipment, mechanical equipment, chemical equipment, etc. Refers to all linear (including cylindrical) and planar defects that are open on the surface of a member, and the depth and depth of the defect
There is no problem with the shallowness, the slope of the defect, the shape and dimensions of the tip of the defect, the size of the opening width, etc. Furthermore, the term solid as used in the present invention refers to objects including metals and non-metals (glass, ceramics, concrete, synthetic resins, rubber, etc.) through which ultrasonic waves can be propagated. Further, the depth of the surface open defect referred to herein refers to the vertical distance from the surface of the solid where the defect is open to the tip of the defect. [Background of the Invention] In the field of application of the present invention, parts or members constituting a device are investigated for the presence or absence of defects, and if a defect occurs, the location, shape, size, etc. of the defect are investigated. Detailed defect information is required depending on the nature and type of defect. Information regarding this defect is important and indispensable for strength analysis and life calculation of not only parts or members but also the entire device. For this reason, various flaw detection methods have been developed and put into practical use depending on the nature and type of the defect. Regarding linear or planar defects with openings on the surface of a solid, that is, surface opening defects, a nondestructive method for detecting the location, distribution, and approximate size of the defects is to use X-rays, γ-rays, etc. Various flaw detection methods that utilize physical energy are provided, including radiographic transmission, magnetism, electrical induction, solution penetration, and ultrasonic methods described below, and are used depending on the material, shape, and dimensions of the object to be inspected. There is. However, at present, no method has been developed that can easily measure the depth of surface opening defects with high accuracy and in real time. Incidentally, surface opening defects are defects generally referred to as cracks or cracks, and there are many types and properties thereof. For example, weld cracks that occur in weld metal or heat-affected zones, fatigue cracks in stress concentration areas of parts, quench cracks during heat treatment, place cracks in parts that retain residual stress, and grain boundaries that occur at relatively high temperatures. Each type is classified according to the conditions and environment in which it occurs, such as cracks and stress corrosion cracks that tend to occur in austenitic stainless steel. Conventionally, methods for measuring the depth of these various surface opening defects include
Radiographic inspection methods that utilize the aforementioned radiographic transmission have been widely used. However, in this method,
Transmission photographs of the subject are required, and the test results will depend on the quality of the photographs taken.
High resolution prints must be produced. However, depending on the shape and size of the object, it may not be possible to take a photograph, and even if it is possible to take a photograph, the sensitivity of the film and the strength of the radiation energy must be selected depending on the object, and handling may be difficult. It also has the special safety problem of radiation exposure, and many requirements are required for measurement. For this reason, it is often impossible to measure easily and accurately. On the other hand, it has been reported that methods using ultrasonic waves have already been put into practical use ("Ultrasonic Flaw Detection Test B" published by the Japan Nondestructive Inspection Association in 1979, pp. 117-118, "Nondestructive Inspection" No. 32) Volume 2, February 1983, pages 110-111)
However, the methods are few and limited. The above report will be explained below with reference to FIGS. 11 to 14. The above report uses a method called the edge peak echo method, and the outline of the method will be explained with reference to FIGS. 11 and 12. In the figure, reference numeral 1 denotes an object to be inspected, and a planar defect 1a with an opening and a depth d is provided on the surface of the object. 1b is the flaw detection surface of the test object 1, 1c is the tip of the defect 1a, and 1d is the bottom surface (anti-flaw detection surface) of the test object 1. Reference numeral 20 denotes a normal bevel probe or a point-focusing bevel probe (hereinafter referred to as bevel probe), which is in contact with the flaw detection surface 1b and is pointed at arrow A or so as to capture the echo from the tip 1c of the defect. Emit ultrasonic waves while scanning back and forth in direction B. 20
a and 20b indicate arbitrary positions when the angle probe 20 is scanned back and forth. Now the angle probe 20 is 20
When scanning from position a in the direction of arrow B, the 12th
On the CRT 4 in the A scope display shown in the figure, the echo height from the defect 1a is displayed as it changes continuously so that it gradually becomes lower as the angle probe 20 moves, and an echo envelope 50 is obtained. . In this case, when the beam axis 30 of the angle probe 20 enters the tip 1c of the defect, a slight peak echo 60 is obtained at a position on the CRT 4 corresponding to the beam path length x, and the echo envelope 50 shows that position. Is displayed. The edge peak echo method uses the beam path x at the position of the peak echo 60 from the tip 1c of the defect, and the angle probe 20.
In this method, the depth d of the defect is determined geometrically from the refraction angle θ as d=x·cos θ. In the report, under the measurement condition that the angle α between the incident direction of the ultrasonic wave and the surface of the defect 1a is 10° or more, the refraction angle θ = 45° to more clearly identify the peak echo 60.
It is noted that it is better to use a normal bevel probe, or a point-focusing bevel probe or split-type probe that can narrow down the sound waves, and if the depth d of the defect is relatively large. , it is stated that it is possible to estimate the depth d with an accuracy of approximately ±2 mm. However, it has been reported that when another defect is attached to the tip 1c of the defect, the measurement accuracy decreases. This report is a report conducted by the inventors of the present application, in which various experiments were conducted on the influence of the shape and size of the tip of a defect on the height (depth) of the defect, as a study on the edge peak echo method. Figure 13 shows the test object and the experimental procedure, in which a bevel was taken on a 65 mm thick steel plate and a penetration failure part of depth d was created.
CO ₂ semi-automatic butt welding. The same reference numerals as in FIG. 11 indicate the same things. The flaw detection surface 1b is finished smooth (ⓓ), and the defect depth d is approximately 30 mm. The experiment was first conducted by comparing the shape and size of the tip 1c of the three types of defects shown in FIG.
d _R = measurement error Δd].
The shape of the tip of the defect shown in Figure 14 is a schematic enlargement of the tip 1c of the defect in Figure 13, and its size is 2ρ (unit: mm) defined as shown in the figure.
It is. The experimental results show that there is almost no difference in shape, and when 2ρ is less than about 1 mm, Δd can be measured with an accuracy of about ±3 mm, but when 2ρ exceeds 1 mm, the accuracy suddenly deteriorates. Next, the measurement accuracy of the defect height (depth) d was tested using different types of probes. The experimental results are shown in the table below. In the table, n is the number of samples, is the average value of the measurement error, and σ is the standard deviation of the measurement error.

[Purpose of the invention]

The present invention solves the problems of the prior art described above, and the depth of surface opening defects occurring in solids can be reduced by
Ultra-high-precision measurement that can be easily and accurately measured without being affected by the depth or shallowness of the defect, the inclination of the defect, the shape and size of the tip of the defect, the size of the opening width of the defect, etc., and can be measured in real time. The purpose of the present invention is to provide a method for measuring the depth of a surface opening defect in a solid using sound waves. [Summary of the Invention] The present invention is a method for measuring the depth of an open defect on the surface of a solid using ultrasonic waves. A vertical probe is brought into contact with the probe, and a longitudinal ultrasonic wave is incident from the vertical probe toward the tip of the aperture defect almost perpendicularly to the surface, and the incident wave reaches the tip of the aperture defect and causes the tip to Electric devices, mechanical devices, etc. are constructed by receiving scattered waves as a sound source into the vertical probe and measuring the depth of a surface aperture defect using the received scattered wave propagation time as an evaluation index. The present invention relates to a method that can easily measure the depth of surface opening defects occurring in parts and members non-destructively, with high precision, and in real time. [Embodiment of the Invention] A first embodiment of the present invention will be described with reference to FIGS. 1 to 8. In the figures, the same reference numerals as in FIGS. 11 and 12 indicate the same things.
In FIG. 1, 2 is a longitudinal wave vertical probe (hereinafter referred to as a vertical probe), and the surface opening defect 1a of the object 1 is
It is in contact with the flaw detection surface 1b directly above the flaw detection surface 1b, and is connected to a pulse reflection type ultrasonic flaw detector (hereinafter referred to as an ultrasonic flaw detector) 3 indicated by an A scope via a high frequency cable. The surface opening defect in this example is a planar defect and is oriented almost perpendicularly to the flaw detection surface 1b.
This is a defect with a depth d _R where the tip of the defect is linear. Now, if a longitudinal ultrasonic wave is incident almost perpendicularly from the vertical probe 2 toward the tip 1c of the defect, if there is no surface aperture defect 1a, the ultrasonic wave will be emitted as shown in Fig. 2. , with the directivity determined by the frequency (wavelength) of the vertical probe 2 and the transducer dimensions,
The beam 6 shown by the dotted line propagates through the object 1, reaches the bottom surface 1d of plate thickness t, is reflected, and is received by the vertical probe 2 again. 7 is an incident wave, and 8 is a bottom reflected wave. However, when there is a surface opening defect 1a, the tip 1c of the defect becomes a sound source, as shown in FIG. 3, and when the incident wave 7 in FIG. 2 reaches the tip 1c, the tip is excited and the incident wave wave 7 is 2
The cylindrical waves 9 are scattered dimensionally, and the scattered cylindrical waves 9 are propagated within the subject 1. A part of the cylindrical wave 9 is connected to the vertical probe 2
The echo of the received cylindrical wave 9 is
When displayed on the CRT 4, an echo pattern as shown in FIG. 4 is obtained. In other words, CRT4
The transmission pulse T is displayed at the origin on the time axis _of
An echo F of the cylindrical wave 9 is displayed at a position d _u on the time axis corresponding to , and a bottom echo B is displayed almost simultaneously at a position t _u corresponding to the plate thickness t. In this case, the position of each displayed echo will display the depth _dR and plate thickness t of the surface aperture defect 1a as is, although it includes a slight measurement error that will be described later. Unaffected by shallowness, inclination, tip shape and size, opening width, etc.
The depth d _R of the defect can be measured from the propagation time d _u of the echo F caused by the cylindrical wave 9 . Figure 5 is a diagram showing the shape and dimensions of the test object used in this example.
A slit is made in the center of a 100mm steel plate (material SS41) by electrical discharge machining with a width of 1.0mm and a varying depth _dR . The number of samples is 12, and the depth d _R is 1.0, 2.0,
3.0，5.0，7.0，10.0，20.0，30.0，40.0，50.0，
There are 12 types: 60.0 and 70.0 mm. Furthermore, the tip a of the slit is machined to have an radius of 0.5 mm as shown in Fig. 6. The slit depth _dR is measured using the first method described above.
The test was carried out as shown in the figure. The frequency of the vertical probe used was 5MHz. First, as shown in Figure 2, the vertical probe is brought into contact with the surface of the steel plate where there are no slits, and the bottom echo height is taken as the reference sensitivity (0 dB) on the CRT. Next, the vertical probe is moved so that it touches directly above the slit as shown in Figure 3, and the echoes of the cylindrical waves scattered from the tip of the slit are displayed on the CRT. Echo height h of the displayed cylindrical wave
Figure 7 shows the relationship between the slit depth _dR (unit: dB) and the slit depth dR (unit: mm). In the figure, the horizontal axis is the slit depth.
d The logarithm value of _R , the vertical axis is the echo height h, and the circle mark is the measured value. Furthermore, the dotted line in the figure indicates the noise region, and its value is approximately -75 dB. When a regression equation is obtained for each measured value using the least squares method, h=-22 log d _R -19.5. The above equation becomes a straight line shown by the chain line in the figure, and it can be seen that there is a good correlation between the two. This correlation agrees well with the distance amplitude characteristic h∝1/d _R of the scattered waves. The measurable limit of the slit depth d _R is theoretically up to the point P where the chain line of the regression equation intersects with the dotted line of the noise region, and in the case of this embodiment, it can be estimated that it is possible up to about 300 mm. Next, the measurement accuracy in this example will be explained with reference to FIG. In the figure, the horizontal axis is the actual slit depth d _R (unit:
mm), and the vertical axis is the slit depth d _U (unit: mm) obtained from the regression equation obtained by the method of the present invention, and the ○ mark is the value. As a result, it can be seen that the two values match very well and that highly accurate measurement can be performed. The average value of error is +0.058mm, and the standard deviation of error σ is 0.211mm.
The correlation γ between d _R and d _U is 0.99997, showing a very good correlation. In the first embodiment, a case was explained in which an opening defect with good machining accuracy was artificially provided in the test object, but below, with reference to FIGS. A second example of an opening defect occurring at an end will be described. The test object used in this example was 25 mm thick as shown in Figure 9.
Web of height 50mm x length 100mm and board thickness 25mm x width
A 250mm x 100mm long flange is T-welded, and a fatigue crack has occurred at the weld toe on the flange side. Materials are both web and flange.
It is SM50 (JIS G3106). Crack depth d _R is 0.8
There are 13 types from mm to 9.3mm. Since the vertical probe 2 could not be brought into contact directly above the crack, the measurement was carried out by bringing it into contact with the crack as shown in FIG. The measurement results are shown in FIG. In the figure, the horizontal axis is the actual crack depth d _R (unit: mm), the vertical axis is the crack depth d _U (unit: mm) measured by the method of the present invention, and the circles indicate the measured values. Both agree very well, mean measurement error = -0.062mm, standard deviation of error σ = 0.266mm
The correlation γ between d _R and d _U is 0.868, showing a very good correlation. The surface opening defect in the first and second embodiments described above is a planar defect, and the tip of the defect has a linear length, but the surface opening defect is a linear defect, If the tip of the defect is point-shaped, the scattered waves scattered from the tip of the defect spread three-dimensionally and become spherical waves, part of which is received by the vertical probe, as shown in Figure 4. The difference is that a spherical wave echo is displayed at a position corresponding to the depth of the surface aperture defect from the position of the transmitted pulse T, and a bottom echo is displayed almost simultaneously at a position corresponding to the plate thickness. Just,
The depth of the defect is measured from the propagation time of the echo caused by the spherical wave, and other measurement methods are the same. [Effects of the Invention] As explained above, the present invention brings a vertical probe into contact with the surface of an aperture defect opened on the surface of a solid,
A longitudinal ultrasonic wave is incident from the vertical probe toward the tip of the aperture defect almost perpendicularly to the surface, and the incident wave reaches the tip of the aperture defect and is scattered using the tip as a sound source. The wave is received by the vertical probe, and the depth of the aperture defect is measured using the propagation time of the received scattered wave as an evaluation index.
The depth of a surface opening defect can be easily determined with high precision and in real time without being affected by the depth or shallowness of the defect, the slope of the defect, the shape and size of the tip of the defect, or the size of the opening width of the defect. can be measured.

[Brief explanation of drawings]

1 to 8 are explanatory diagrams of the first embodiment of the present invention, FIG. 1 is a schematic explanatory diagram of the measurement method of the present invention, and FIG. Figure 3 is an illustration of the scattered waves scattered from the tip of the surface aperture defect, Figure 4 is a diagram showing the echo pattern on the CRT obtained in the case of Figure 3, Fig. 5 is a diagram showing the shape and dimensions (unit: mm) of the subject used in this example, Fig. 6 is an enlarged view of section a in Fig. 5, and Fig. 7 is a diagram showing the
FIG. 8 is a diagram showing the relationship between the echo height and the defect depth of the object to be examined and the measurable limit, and is an explanatory diagram of the measurement accuracy in this example. FIG. 9 and FIG. 10 are explanatory diagrams of the second embodiment of the present invention,
FIG. 9 is an explanatory diagram for measuring surface opening defects occurring at the weld toe of a welded joint, and FIG. 10 is an explanatory diagram of the measurement accuracy of the values measured by the method of FIG. 9. Figures 11 to 14 are explanatory diagrams regarding the conventional edge peak echo method. Figure 11 is a schematic explanatory diagram of the edge peak echo method for measuring the depth of surface aperture defects, and Figure 12 is the diagram shown in Figure 11. Figure 13 is an explanatory diagram showing the effect of the shape and size of the tip of a defect on the depth of the defect in the edge peak echo method, and Figure 14 is a diagram showing the echo pattern on a CRT obtained by the method of FIG. 3 is a diagram schematically defining the tip shape and size of a defect. 1...Object to be inspected, 1a...Surface opening defect, 1b...
...Flaw detection surface, 1c...Tip of defect, 1d...Bottom surface,
2... Vertical probe, 3... Ultrasonic flaw detector, 4...
CRT, 9...scattered waves, 20...bevel probe, 3
0...beam axis, 50...envelope, 60...peak echo.

Claims (1)

[Claims] 1. A vertical probe is brought into contact with the surface of an aperture defect opened on the surface of a solid, and a longitudinal wave is emitted from the vertical probe almost perpendicularly to the surface toward the tip of the aperture defect. Inject an ultrasonic wave, the incident wave reaches the tip of the aperture defect, the scattered wave is received by the vertical probe using the tip as a sound source, and the propagation time of the received scattered wave is used as an evaluation index. A method for measuring the depth of surface open defects in solids. 2. A vertical probe is brought into contact with the surface of an open defect where the tip of the defect opening on the surface of the solid is dotted, and the probe is vertically moved from the vertical probe almost perpendicularly to the surface toward the tip of the open defect. Inject an ultrasonic wave, the incident wave reaches the tip of the aperture defect, the tip is used as a sound source, and the scattered spherical wave is received by the vertical probe, and the propagation time of the received spherical wave is evaluated. A method for measuring the depth of surface opening defects in solids as an indicator. 3. A vertical probe is brought into contact with the surface of the open defect where the tip of the defect opening on the surface of the solid is linear, and the vertical probe is vertically moved from the vertical probe almost perpendicularly to the surface toward the tip of the open defect. Inject an ultrasonic wave, the incident wave reaches the tip of the aperture defect, the tip is used as a sound source, and the scattered cylindrical wave is received by the vertical probe, and the propagation time of the received cylindrical wave is evaluated. A method for measuring the depth of surface opening defects in solids as an indicator.